Dental bridges comprising fiber reinforced frameworks with fiber or particulate reinforced veneers

ABSTRACT

A dental restoration comprising a fiber reinforced composite framework and one or more of a randomly dispersed, fiber-filled veneer, a soft particulate filled composite veneer having a strain to failure greater than that of FRC framework and/or a brittle particulate filled composite veneer having a strain to failure value less than that of the FRC framework. The fiber filled veneer is advantageously placed beneath the framework, the soft veneer is advantageously pled where tensile stresses are expected to occur, while the brittle particulate filled veneer is placed where compressive stresses are expected to occur.

This application claims priority to Provisional Application Ser. No.60/078,347 filed on Mar. 17, 1998 which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to composite materials for dental restorations.In particular, this invention relates to fiber reinforced prosthodonticframeworks comprising a fiber reinforced composite framework and atleast one or more filled composite veneers.

2. Brief Discussion of the Art

Fiber-reinforced composites have found increasing use in the field ofmaterials for dental restorations, and are described, for example, inU.S. Pat. Nos. 4,717,341 and 4,894,012 to Goldberg et al. both of whichare hereby incorporated by reference in their entirety. Fiber-reinforcedcomposites generally comprise at least two components, a polymericmatrix and fibers embedded within the matrix. The polymeric matrix maybe selected from those known for use in composite dental materials, forexample polyamides, polyesters, polyolefins, polyimides, polyarylates,polyurethanes, vinyl esters or epoxy-based materials. The fibers used toreinforce composite material may comprises glass, carbon, or polymerfibers such as polyaramide and polyethylene, as well as other naturaland synthetic fibers.

Fiber reinforced composite material provides several advantages, mostnotably increased strength and stiffness. As described in U.S. Pat. Nos.4,717,341 and 4,894,012 to Goldberg et al., such materials accordinglyare used as structural components in a variety of dental appliances,taking the form of bars, wires, beams, posts, clasps, and laminates foruse in traditional bridges, crowns, artificial teeth, dentures, veneers,and the like. They have also been used in connection with orthodonticretainers, bridges, space maintainers, splints, and the like. In theseapplications, the fibers preferably take the form of long, continuousfilaments, although the filaments may be shorter than 5 millimeters.Where the composites take the form of elongated wires, the fibers are atleast partially aligned and oriented along the longitudinal dimensionsof the wire. However, depending on the end use of the compositematerial, the fibers may also be otherwise oriented, including beingnormal or perpendicular to that dimension.

Fiber reinforced composites are particularly useful as structuralcomponents in dental bridges. In the dental arts, a bridge is a devicefor the restoration and replacement of one or more natural teeth,replacing at least one missing tooth and supported on either side by theremaining teeth. A bridge generally comprises a pontic for replacementof the missing tooth, and a connector on either side of the pontic whichconnects the pontic to a retaining member such as a crown formed on anabutment tooth adjacent the pontic. By their nature, bridges must beaesthetic, as well as strong, in order to withstand forces generated bychewing and to maintain the positions of the abutting teeth.

The combination of a fiber reinforced framework and particulate filledcomposite veneer offers good strength and excellent aesthetics. Thesesystems result in a decrease in the antagonistic wear of opposite teethcompared to the use of metal-porcelain bridges. These systems alsoprovide higher impact energy, and are free of leaching of metal ions.The tensile strength and elastic modulus of uniaxially orientedcontinuous glass fiber reinforced BIS-GMA are competitive with those ofstainless steel and some titanium alloys. Such bridges are described forexample in co-assigned U.S. Provisional Patent Application No.60/055,590, filed Aug. 12, 1997, and exemplified by the FIBREKOR® systemfor making dental bridges commercially available from Jeneric/PentronInc., Wallingford, Conn.

An important consideration in constructing a single or multi-unit bridgeare the forces exerted on the bridge. Dental restorations must be ableto withstand the normal mastication forces and stresses that existwithin an oral environment, which have been described, for example, in“Restorative Dental Materials”, 4th ed., edited by F. A. Peyton and R.G. Craig, pp. 121-133 (1971). Different stresses are observed duringmastication of different types of food, which can be experimentallymeasured by placing, for example, a strain gauge in inlays on the tooth.Stresses differ depending not only on the type of food, but also on theindividual. For example, stress values may range from 570 to 2300lb./inch² or from 950 to 2400 lb./inch² for a single thrust. Thephysical properties of dental restorations must be adequate to withstandthe stresses applied by the repetitive forces of mastication. If anapplied force exceeds that which the dental restoration can withstand,then fracture in the dental restoration material results. Therefore, thedental restoration must be constructed so that loads on the restorationare lower than the maximum load-bearing capability of the restoration.

An important parameter in dental bridges in particular is the flexuralstrength of such bridges. In a multi-unit dental bridge there is atleast one pontic not supported on its gingival surface. The onlysupports are the two connecting areas with the adjacent abutments. Henceif a load is applied normal to any pontic surface, the bridge tends todeflect, resulting compressive stress/strain on the surface on whichload is applied and tensile stress/strain on the opposite surface. Thisis common for any simply-supported specimen exposed to flexural testing.Because of the geometric complexity of the dental bridge and themultidirectional loads generated in different locations during chewingand mastication, the magnitudes of stress/ strain vary in differentlocations.

Consequently, while well-suited for their intended purposes, the designof many currently manufactured dental bridges suffers from a frameworkmaterial having a flexural modulus higher than that of theparticulate-filled veneer material; and/or the particulate-filled veneermaterial having a strain to failure value lower than that of thefiber-reinforced framework material. There is a need to make theparticulate filled composites compatible with the fiber reinforcedcomposite structural frameworks in the strain to failure value toprovide high strength to the dental restoration. It is desirable toincrease strength of dental restorations without complicating orincreasing the number of steps used in the fabrication of dentalrestorations. Such improvements would result in dental bridges which canbetter withstand the forces and strains that accompany the chewing offood and other activities, and which provide maximum performance fortheir intended use.

SUMMARY OF THE INVENTION

The above-described drawbacks and deficiencies of the prior art arealleviated by the fiber reinforced prosthodontics of the presentinvention, wherein the prosthodontic may include a fiber-reinforcedcomposite structural component or framework and a veneer comprising afiller of particulate and/or randomly dispersed fibers. The veneer maybe a “brittle” veneer of particulate filled composite having a strain tofailure value less than that of the fiber reinforced framework and/or a“soft” veneer of particulate filled composite having a strain to failurevalue greater than that of the fiber reinforced framework. In animportant feature of this embodiment, the prosthodontic is constructeddepending on its intended location within the patient's mouth, and thusthe expected forces that will impact the prosthodontia. In particular, asoft particulate filled composite having a higher deflection value thanthe fiber reinforced composite is used in the areas where higher tensilestrain is expected. On the other hand, a hard particulate filledcomposite having a high compressive strength is used in areas subject tohigh compressive strain and wear.

In another embodiment, a soft particulate veneer is provided whichcomprises randomly dispersed fibers. The fibers may have a maximumlength of about ¼ inch, preferably in a range of from about 0.01 toabout 6 millimeters, and more preferably in the range of from about 20to about 1000 microns and a diameter below about 20 microns, preferablyin the range of from about 5 to about 10 microns. The veneer has strainto failure values compatible with the fiber reinforced compositestructural components and/or frameworks.

A dental bridge is further provided using a unidirectional fiberreinforced composite structural component wherein the interior portionof the pontic and the abutments is fabricated of the randomly dispersedfiber filled composite resin disclosed herein.

In yet another embodiment herein, a process for manufacturing a dentalrestoration comprises providing a structural component for use as theframework of a dental restoration such as a bridge. Composite resinfilled with a fibrous filler of randomly dispersed fibers is disposedunderneath and on the structural component in the form of pontics andabutments and cured thereon to form a framework for a dental bridge. Thebridge is given the final anatomical contour by veneering with aparticulate filled composite.

In still another embodiment herein, a crown having an interior segmentof this randomly-dispersed fibrous filled composite is fabricated.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there are shown in thedrawing forms which are presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown. Referring now to the drawings wherein likeelements are numbered alike in the several FIGURES:

FIG. 1 is a perspective view of a unidirectional fiber-reinforcedstructural component (framework) and a fiber-filled composite veneer inthe shape of a pontic in accordance with the present invention;

FIG. 2 is a perspective view of the testing arrangement utilized tomeasure three-point bend strength of various samples;

FIG. 3 is a perspective view of the testing arrangement utilized tomeasure three-point bend strength of various samples;

FIG. 4 is a perspective view of a dental bridge of the prior art locatedin the mandibular portion of the mouth;

FIG. 5 is a perspective view of a fracture pattern in a prosthodonticsmaterial having a fiber reinforced framework component and a brittleparticulate filled composite component; and

FIG. 6 is a perspective view of a fracture pattern in a prosthodonticsmaterial having a fiber reinforced framework component and a softparticulate filled composite component.

DETAILED DESCRIPTION OF THE INVENTION

The prosthodontic dental restoration in accordance with the presentinvention comprises a fiber reinforced composite (hereinafter “FRC”)structural component or framework and may include at least one veneer.As used herein, “veneer” is used to refer to that part of therestoration comprising a randomly dispersed, short fiber-filled and/orparticulate-filled composite, as distinguished from the FRC. In oneembodiment, the veneer comprises a randomly dispersed, shortfiber-filled and/or particulate-filled composite (hereinafter “PFC”)having a strain to failure value greater than that of the fiberreinforced framework, referred to herein as a “soft” PFC. The dentalrestoration may further comprise a veneer of a particulate-filledcomposite having a strain to failure value less than that of the FRCframework, referred to herein as a “brittle” PFC. As will be describedin more detail below, the placement of the soft and brittle PFCs ontothe framework depends on the intended location of the prosthodontia inthe patient's mouth, which affects the type and degree of stress/strainplaced on the prosthodontia.

In another embodiment, the veneer comprises a polymeric matrix componentand a fibrous filler component wherein the fibers are less than about ¼inch in length and are randomly-dispersed in the resin. Preferably, theveneer is fabricated around the structural component as in a ponticand/or as abutments.

The FRC structural component of the present invention comprises apolymeric matrix and fibers embedded within the matrix. The polymericmatrix is selected from those known in the art of dental materials,including but not being limited to polyamides, polyesters, polyolefins,polyimides, polyarylates, polyurethanes, vinyl esters or epoxy-basedmaterials. Other polymeric matrices include styrene, styreneacrylonitrile, acrylonitrile butadiene styrene polymers (“ABSpolymers”), polysulfones, polyacetals, polycarbonates, polyphenylenesulfides, and the like.

Preferred matrix materials include those based on acrylic andmethacrylic monomers, for example those disclosed in U.S. Pat. Nos.3,066,112, 3,179,623, and 3,194,784 to Bowen; U.S. Pat. Nos. 3,751,399and 3,926,906 to Lee et al.; and commonly assigned U.S. Pat. No.5,276,068 to Waknine, all of which are herein incorporated by referencein their entirety. An especially preferred methacrylate monomer is thecondensation product of bisphenol A and glycidyl methacrylate, 2,2′-bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane (hereinafterabbreviated “BIS-GMA”). Polyurethane dimethacrylates (hereinafterabbreviated “PUDMA”) are also commonly-used principal polymers suitablefor use in the present invention.

Use of an ethoxylated bisphenol A dimethacrylate allows the relativeamounts of dimethacrylate oligomer to be decreased in comparison toother resin formulations, for example those disclosed in U.S. Pat. Nos.5,276,068 and 5,444,104 to Waknine. Use of the ethoxylated monomer alsounexpectedly improves the wettability of the cured resin composition,thereby resulting in better filler incorporation. The cured resins thusobtained have improved water sorption characteristics, improved stainresistance, and further possess excellent wearability.

The ethoxylated bisphenol A dimethacrylate in accordance with thepresent invention has the structure

CH₂═C(CH₃)CO₂(C₂H₄O)_(x)C₆H₄C(CH₃)₂C₆H₄(OC₂H₄)_(y)O₂CC(CH₃)═CH₂

wherein x+y is an integer from 2 to 20, and preferably from 2 to 7. Suchmaterial is available from Sartomer®, under the trade name SR348 orSR480, or from Esschem.

The preferred dimethacrylate oligomer for use with the ethoxylatedbisphenol A dimethacrylate of the present invention is a polycarbonatedimethacrylate condensation product obtained by the condensationreaction of a hydroxy alkyl methacrylate of the general formulaH₂CC(CH₃)C(O)O—A—OH, in which A is a C₁-C₆ alkylene, with 1 part of abis(chloroformate) of the formula ClC(O)—(OR)_(n)—OC(O)Cl, in which R isa C₂-C₅ alkylene having at least two carbon atoms in its principalchain, and n is an integer from 1 to 4. By “principal chain” is meantthe chain of carbon atoms serving as a bridge between the oxygen atoms.Such preferred polycarbonate dimethacrylate condensation products havebeen described in commonly assigned U.S. Pat. Nos. 5,276,068, and5,444,104, the disclosures of both of which are herein incorporated byreference. A particularly preferred polycarbonate dimethacrylate is thecondensation product of 2-hydroxyethylmethacrylate (2-HEMA) andtriethylene glycol bis(chloroformate).

In addition to the two aforementioned monomeric components, the resinousdental compositions of the present invention can further include adiluent monomer to increase the surface wettability of the compositionby decreasing the viscosity of the polymerization medium. Suitablediluents include those known in the art such as hydroxy alkylmethacrylates, for example 2-hydroxyethyl methacrylate and2-hydroxypropyl methacrylate; ethylene glycol methacrylates, includingethylene glycol methacrylate, diethylene glycol methacrylate,tri(ethylene glycol) dimethacrylate, fluoro-triethylene glycoldimethacrylate, and tetra(ethylene glycol) dimethacrylate;diisocyanates, such as 1,6-hexamethylene diisocyanate and ethoxylatedmonomers such as 1,6-hexanedioldimethacrylate. Tri(ethylene glycol)dimethacrylate (TEGDMA) is particularly preferred.

The polymer matrix typically includes polymerization initiators,polymerization accelerators, ultra-violet light absorbers,anti-oxidants, and other additives well known in the art. The polymermatrices may be visible light curable, self-curing, dual curing, andvacuum, heat, and pressure curable compositions as well as anycombination thereof. The visible light curable compositions include theusual polymerization initiators, polymerization accelerators,ultraviolet absorbers, fluorescent whitening agents, and the like. Forexample, visible light curable compositions employ light-sensitivecompounds such as benzil diketones, and in particular, DL-camphorquinonein amounts ranging from about 0.05 to 0.5 weight percent. Self-curingcompositions will generally contain free radical polymerizationinitiators such as, for example, a peroxide in amounts ranging fromabout 0.5 to 6 weight percent. Particularly suitable free radicalinitiators are lauryl peroxide, tributyl hydroperoxide and, moreparticularly benzoyl peroxide.

The polymerization accelerators suitable for use in the compositions ofthis invention are the various organic tertiary amines well known in theart. In visible light curable compositions, the tertiary amines aregenerally acrylate derivatives such as dimethylaminoethyl methacrylateand, particularly, diethylaminoethyl methacrylate in amounts rangingfrom about 0.05 to 0.5 weight percent. In the self-curing compositions,the tertiary amines are generally aromatic tertiary amines, such asdimethyl-p-toluidine, dihydroxyethyl-p-toluidine and the like, inamounts ranging from about 0.05 to about 4.0 weight percent.

It is furthermore preferred to employ an ultraviolet absorber in theseresinous adhesives in amounts ranging from about 0.05 to about 5.0weight percent. Such UV absorbers are particularly desirable in thevisible light curable compositions in order to avoid discoloration ofthe resin from any incident ultraviolet light. Suitable UV absorbers arethe various benzophenones, particularly UV-9 and UV-5411 available fromAmerican Cyanamid Company, and benzotriazoles known in the art,particularly 2-(2′-hydroxy-5′-methylphenyl)-benzotriazole, sold underthe trademark TINUVIN P by Ciba-Geigy Corporation, Ardsley, N.Y. In theself-curing compositions, the polymerization accelerator can be includedin the resinous composition which is used for pretreating the exposeddentin. The heat and pressure curable compositions, which are generallyfilled compositions, include, in addition to the monomeric components, aheat cure initiator such as benzoyl peroxide, 1,1′-azobis(cyclohexanecarbonitrile), or other free radical initiators. Thereinforcing fiber element of the fiber-reinforced composite preferablycomprises glass, carbon, graphite, polyaramid, or other fibers known inthe art. The FRC fibers are greater than about 100 microns, preferablygreater than about 5 mm, and more preferably greater than about 10 mm,and, in contrast to the randomly dispersed fiber-filled composite veneerdescribed below, they are not randomly dispersed. Thus, in oneembodiment of the present invention, the fibers take the form of long,continuous filaments which are at least partially aligned relative toeach other. Where the composites take the form of elongated bars, thefibers are at least partially (and preferably fully) aligned andoriented along the longitudinal dimensions of the bar. However,depending on the end use of the composite material, the fibers may alsobe otherwise oriented at various angles between 0 and 90° to thelongitudinal fibers.

The amount of reinforcing fibers used within the composite will dependon the particular application, but preferably comprises at least about20% by weight of the composite material. A preferred FRC for use in thepresent invention is glass fiber reinforced resin, commerciallyavailable under the trade name FIBREKOR® from Jeneric/Pentron, Inc.,Wallingford, Conn. Other suitable fibers for FRCs in accordance with thepresent invention include high modulus, organic polymeric fibers, forexample polyethylene fibers (available from Allied under the trade nameSPECTRA) or aramid fibers (available from DuPont under the trade nameKEVLAR). Preferably, the reinforcing fibers are used in accordance withU.S. Pat. Nos. 4,717,341 and 4,894,012 to Goldberg et al., the relevantportions of which are herein incorporated by reference. The polymericmatrix may further contain the particulate fillers described below inamounts of up to about 5% by weight of the total composite.

2. Veneers

The veneers of the invention comprise a polymeric matrix and may includeone or more fillers embedded in the matrix. Preferably the veneers arefilled with particulate filler and are referred to as Particulate FilledComposite (PFC) Veneers.

In one embodiment, the prosthodontics of the present invention compriseone or more veneers, a soft PFC veneer having a strain to failure valuegreater than that of a fiber reinforced framework, and a brittle PFChaving a wear resistance similar to natural enamel. Each PFC comprises apolymeric matrix and a particulate filler.

Polymeric matrices suitable for use in the veneers are similar to andinclude those described above in connection with the FRC framework.Preferably, the FRC and PFC matrices are identical or compatible, e.g.,all being methacrylate based.

Suitable particulate fillers are those capable of being covalentlybonded to the polymeric matrix itself or to a coupling agent that iscovalently bonded to both and can include all of the inorganic fillerscurrently used in dental restorative materials. Examples of suitableparticulate filling materials include but are not limited to those knownin the art such as silica, silicate glass, quartz, barium silicate,barium sulfate, barium molybdate, barium methacrylate, strontiumsilicate, barium borosilicate, strontium borosilicate, borosilicate,lithium silicate, amorphous silica, ammoniated or deammoniated calciumphosphate and alumina, zirconia, tin oxide, and titania. Particularlysuitable particulate fillers for dental filling-type materials preparedin accordance with this invention are those having a particle sizeranging from about 0.1 to about 5.0 microns may be prepared by a seriesof milling steps comprising wet milling in an aqueous medium, surfaceetch milling and silanizing milling in a silane solution. Some of theaforementioned inorganic filling materials are disclosed incommonly-assigned U.S. Pat. Nos. 4,544,359 and No. 4,547,531 to Waknine,the pertinent portions of which are incorporated herein by reference.Details of the preparation of the preferred inorganic particulatefiller, which comprises a mixture of from about 5 to about 20% by weightof borosilicate glass and from about 80 to about 95% by weight bariumborosilicate, and has an average particle size diameter of from about0.5 to about 5 microns, can be found in the aforementioned U.S. Pat.Nos. 4,544,539 and 4,547,531. A microfine silica or silicate of about0.001 to 0.1 may be included to adjust handling and moldingcharacteristics.

Suitable organic filler materials are known in the art, including forexample the poly(methacrylate) fillers described in U.S. Pat. No.3,715,331 to Molnar. A mixture of organic and inorganic filler materialsmay also be used. One consideration in the selection of a filler is thedifference in the index of refraction of the filler material and that ofthe resinous matrix. In general, a more aesthetically pleasingrestoration can be obtained when the difference between the index ofrefraction of the filler material and that of the resin matrix is small.

As discussed above, the brittle PFC has a high compressive strength andwear resistance. The brittle composite is thus preferably place inlocations demanding high wear resistance. In general, the brittle PFC ismore highly filled and polishable, i.e., comprises from about 70 toabout to about 80% by weight filler of the total PFC composition, andhas deflection values in the range from about 0.3 mm to about 0.5 mm astested according to American National Standard/American DentalAssociation Specification No. 27 (“ANSI/ADA Spec. No. 27”) (on samplesof 2 mm in thickness by 2 mm in width by 25 mm in length). A suitablecommercially available material for use as a brittle PFC is availableunder the trade name SCULPTURE® from Jeneric/Pentron, Inc., Wallingford,Conn. This PFC has deflection values of about 0.2 to about 0.5 mm andfurther as shown in Table 3.

The soft PFC has a strain to failure value about equal to or higher thanthe FRC component. The strain to failure values of the soft PFC are thusdependent on the composition and volume fraction of the resin, sizedistribution and amount of fibrous and particulate fillers. In general,the soft PFC is less filled, comprising from about 0 to about 80% byvolume filler, and preferably from about 10 to about 30% by volumefiller of the total composite. A suitable soft PFC having proper strainto failure values can utilize the full support of the FRC composite asdemonstrated in Example 4 below. Generally, the deflection values of thesoft PFC are greater than about 0.5 mm, and preferably range from about0.6 to about 5.0 mm, and more preferably range from about 0.6 to about1.5 mm for a bar having dimensions of 2×2×25 mm as measured by ANSI/ADASpec. No. 27.

In a preferred embodiment, the soft veneer comprises a polymeric matrixwhich is filled or partially filled with a randomly dispersed, fibrouscomponent in addition to the particulate component. The fibrouscomponent may comprise fibers of uniform or random length. The fibrouscomponent preferably comprises short fibers of lengths no greater than ¼inch. Preferably, the length of the fibers is between about 0.01 andabout 6 mm. The fibers are preferably randomly dispersed throughout theresin. The fibers may be fabricated of glass, carbon, ceramic,polyaramid, or other fibers known in the art, such as polyesters,polyamides, and other natural and synthetic materials compatible withthe polymeric matrix. Some of the aforementioned fibrous materials aredisclosed in commonly assigned copending U.S. patent application Ser.Nos. 08/907,177, 09/059,492, 60/055,590 (now issued as U.S. Pat. No.6,039,569), U.S. Ser. No. 08/951,414 (now issued as U.S. Pat. No.6,013,694), and U.S. Pat. Nos. 4,7177,341 and 4,894,012 all which areincorporated by reference herein. The fibers may further be treated, forexample, thermally, chemically or mechanically etched and/or silanized,or otherwise treated such as by grafting functional monomers to obtainproper coupling between the fibers and the resin matrix. Silanizationrenders the fibers hydrophobic, reducing the water sorption andimproving the hydrolytic stability of the composite material, rendersthe fibers organophilic, improving wetting and mixing, and bonds thefibers to the polymeric matrix. Typical silane is A-174 (p-methacrylatepropyl tri-methoxy silane), produced by OSI Specialties, NY.

The polymeric matrix is similar to those described above in connectionwith the FRC framework. Preferably, the matrices are identical orcompatible, e.g., all being methacrylate-based. In a preferredembodiment, the polymeric matrix comprises ethoxylated bisphenol Adimethacrylate in an amount in the range from 55 to about 90 percent byweight of the total resin matrix composition, preferably in an amount inthe range from about 70 to about 80 percent by weight of the total resincomposition. Typically, a dimethacrylate oligomer, preferably theabove-described polycarbonate dimethacrylates, is incorporated into thematrix composition in an amount from about 10 to about 45 weight percentof the total resin composition. The optional diluent monomer istypically present in an amount from about 0 to about 40 weight percentof the total resin composition.

When no diluent component is employed the preferred range for theethoxylated bisphenol A dimethacrylates is from 65 to about 90 weightpercent, and most preferably about 70 weight percent of the total resincomposition, and the preferred range for the dimethacrylate oligomer isfrom about 10 to about 30 weight percent, and most preferably about 30weight percent of the total resin composition.

Typical visible light curable resinous dental compositions according tothis invention comprise:

(a) 10-45 weight percent of the polycarbonate dimethacrylatecondensation product of triethylene glycol bis(chloroformate) and2-hydroxyethylmethacrylate;

(b) 55-90 weight percent of ethoxylated bisphenol A dimethacrylate;

(c) 0.05-0.50 weight percent of DL-camphorquinone;

(d) 0.05-0.5 weight percent of diethylamino ethyl methacrylate; and

(e) 0.05-5 weight percent of TINUVIN P ultraviolet absorber in specificamounts within these ranges to yield about 100% by weight of apolymerization system. A particularly preferred embodiment comprises 68%by weight ethoxylated bisphenol A dimethacrylate, 30% by weight of thepolycarbonate dimethacrylate condensation product of triethylene glycolbis(chloroformate) and 2-hydroxyethylmethacrylate, 0.07% by weight2-(2-hydroxy-5-tert-octylphenyl)bezotriazole, 0.019% by weight2,5-bis(5-tert-butyl-2-benzoxazoyl)thiophene, 0. 193% by weightcamphorquinone, 0.097% by weight benzil, 0.967% by weight2,4,6-trimethyl benzoyldiphenylphosphine oxide, 0.048% by weightbutylhydroxytoluene, 0.242% by weight diethylaminoethyl methacrylate,and 0.967% by weight 1,1,′-azobis(cyanocyclohexane).

Preferred visible light curable compositions comprise the followingcomponents (weight percent) in specific amounts within these ranges toyield about 100% by weight of a polymerization system:

TABLE 1 Broad Preferred Most Range Range Preferred Component 10-45 10-2520 Polycarbonate dimethacrylate condensation product of triethyleneglycol bis(chloroformate) and 2-HEMA 55-90 55-65 60 Ethoxylatedbisphenol A dimethacrylate  0-40 10-30 20 TEGDMA 0.05-0.40 0.200-0.3000.25 Diethylaminoethylmethacrylate 0.25-4.0 0.500-1.500 1.0 TINUVIN P(ultra-violet absorber) 0.05-0.50 0.10-0.30 0.25 2,3-d-bornanedione orDL-camphorquinone  .001-.2500 0.00-0.20 0.05 BHT 0.00-0.500  0.00-0.25000.0097 Fluorescent/whitening agent (UNITEX OB)

The filled and partially filled compositions can be prepared in visiblelight curable formulations, self-curing, and dual curing formulations.In addition, the filled compositions can be prepared in heat pressurecuring formulations. It has surprisingly been found that heat-pressurecuring the filled or partially filled dental compositions of the presentinvention results in a material which exhibits superior physical andmechanical properties when compared to other modes of cure. The filledcomposite restorative materials can be prepared by admixing from about20 to 60% by weight, preferably 25 to 40% by weight, of the unfilledvisible light curable, self-curing, dual-curing or heat-pressure curabledental resin composition with from about 50 to about 80% by weight,preferably about 60 to 75% by weight of inorganic filler (fibrous plusparticulate) material.

In a particularly preferred embodiment, the composite dental restorativematerial comprises a fibrous filler randomly dispersed in the polymericmatrix having an average length of about 0.1 to about 3 mm and aparticulate filler having an average particle size of from about 0.5 to5 microns homogeneously dispersed in the polymeric matrix, with thepolymeric matrix being an organic polymerizable monomeric matrixcomprising the ethoxylated dimethacrylate. In addition, a relativelysmall amount of fumed silica (e.g., below about 15 wt. %) is alsoincorporated within the monomeric matrix to improve handlingcharacteristics. The inorganic filler primarily comprises an X-rayopaque alkali metal or alkaline earth metal silicate such as lithiumalumina silicate, barium silicate, strontium silicate, bariumborosilicate, strontium borosilicate, borosilicate, as well as any ofthe aforementioned materials. For purposes of illustration, and as thepreferred silicate species, barium borosilicate will hereinafter beemployed as being typical of the alkali metal or alkaline earth metalsilicates which can be suitably employed in the present invention. Thebarium borosilicate exhibits an index of refraction close to that of theorganic monomeric matrix in which it is dispersed. The filler canadditionally contain a relatively small amount of borosilicate glasswhich imparts greater compressive strength to the resulting compositeand enhances the translucency thereof thereby enabling better blendingof the restorative material with the adjacent teeth. In addition, thepresence of the borosilicate glass helps narrow the gap in the mismatchof refractive indices between the barium borosilicate inorganic fiberphase and the organic monomeric matrix.

The relative quantities by weight of polymeric matrix, fibrous filler,and particulate filler are set forth in Table 2 below:

TABLE 2 Component Range Preferred Range Most Preferred Polymeric matrix20-60 30-55 30-50 Fibrous Filler  5-50  5-40 10-40 Particulate Filler20-60 20-55 25-45

The deflection values for the soft PFC comprising particulate and randomfibers are generally greater than about 0.5 mm and preferably are in therange of from about 0.6 to about 3 mm and more preferably in the rangeof from about 0.6 to about 1.5 mm for a bar having dimensions of 2×2×25as measured by ANSI/ADA Spec. No. 27. The fibrous filled resin may beused in a variety of ways to manufacture dental materials andrestorations including, but not limited to veneers, cements, crowns,inlays and onlays. Preferably, the fibrous filled resin is used incombination with a structural element or framework comprised of a fiberreinforced composite material to form a dental restoration. The presenceof the fibrous filler in the resin provides improved resiliency andtoughness and thus optimum handling properties and thus, impact strengthof the resin. In one embodiment the randomly dispersed short fiberfilled veneer is used to form a pontic or like structure on top oraround the framework. Attention is directed to FIG. 1 which shows astructural component 10 and a pontic component 12 disposed on component10. Structural component 10 is placed on supporting elements 13 of atesting apparatus. The soft composite herein which is used to formpontic 12 is flexible and easy to shape and mold.

A process for manufacturing a dental restoration comprises providing astructural component for use as the framework of a dental restorationsuch as a bridge. Composite resin filled with a fibrous filler ofrandomly dispersed fibers is disposed on the structural component in theform of a pontic or like form and cured thereon to form a dentalrestoration.

In another embodiment, both the soft PFC veneer and the brittle PFCveneer are used in the manufacture of a bridge to maximize bridgestrength. Accordingly, a brittle PFC veneer (if present) is placed onthat surface of the bridge which is subjected primarily or additionallyto compressive forces. This will generally be on the occlusal surface ofthe bridge, which is subject to masticatory forces. Of course, veneersas presently manufactured may also be substituted in place of thebrittle veneer.

For this reason, it is advantageous to place a soft PFC on the surfaceof the bridge which is expected to undergo primarily or additionaltensile strain, i.e., on the gingival side, which is the side oppositeto the surface subject to masticatory forces. The soft PFC may furtherbe advantageously placed on the gingival half of the restoration. Asshown in FIG. 4, a preferred bridge 40 in accordance with the presentinvention therefore comprises an FRC framework in the form of at leastone bar 42 providing structural support for a bridge support betweenabutment teeth 44, 46. Preferably, the restoration comprises further FRCmaterial 48 wrapped around abutments 44, 46. A brittle PFC veneer 50 isshown in shadow on the occlusal surface 52 of bridge 40, where it willbe subject to compressive stresses arising from mastication. A soft PFCveneer 54 is shown in shadow on the gingival surface of bridge 40, whereit will be subject to atensile strain arising from mastication.

The stress/strain relationship of the materials is important to theembodiments described herein. It is important to note that in additionto the amount of fillers present in the veneers, filler dimensions,filler distribution, size distribution of the fillers, and thestress-strain behavior of the resin all effect the deflection propertiesof the resin. As shown in the formula below, strain is proportional todeflection which is inversely proportional to thickness of the sample.

r=6Dd/L ²

wherein

r=maximum strain at the bottom surface

D=maximum deflection at the center of the beam

L=support span; and

d=thickness of sample

Since the deflection of the veneer is inversely proportional to thethickness, the deflection may increase as the thickness decreases.

The following non-limiting examples further describe the dentalmaterials and restorations of the present invention.

EXAMPLE 1

Three groups of bars were fabricated of different resin filled compositematerials. Group A bars were composed of resin with standard particulatefiller. Group B bars were composed of resin with short fibers randomlydispersed therein as disclosed herein. Group C bars were composed ofresin having longitudinally extending fibers dispersed unidirectionallytherein. Three-point bend testing was performed on the three groups ofbars having dimensions of 4×3×25 mm. The average deflection of Group Abars was 0.44 mm. The average deflection of Group B bars was 0.683 mm.The average deflection of Group C bars was 0.647 mm. The testing showsthat the deflection of the composite used in Group B is slightly greaterthan the deflection of the resin used in Group C. Thus, the resin of theinvention comprising short random fibers is much more compatible thanstandard particulate filled resins to fiber reinforced resins used inthe fabrication of structural components. The testing configuration isshown in FIG. 2 wherein a bar 20 is positioned on fulcrums 22 and a loadin the shape of a ball 24 is applied at the midpoint of the bar tomeasure the bend strength thereof.

EXAMPLE 2

Fiber reinforced structural components in the shape of bars wereprovided and pontics were formed thereon using standard particulatefilled resins (Group A) and using fiber filled resins of the invention(Group B). Three-point bend testing was conducted on Group A and Group Bsamples. Group B samples showed tremendously higher load bearingcapability in comparison to Group A samples. Group A samples averaged aninitial failure at about 141 pounds. Group B averaged an initial failureat about 257 pounds. The testing configuration is shown in FIG. 3wherein a pontic 30 is disposed on a bar 32. Bar 32 rests on fulcrums34. A load in the shape of a ball 36 is applied at the midpoint of thebar to measure the bend strength thereof.

EXAMPLE 3

The advantage of a bridge construction in accordance with the presentinvention is illustrated in three-point-bending flexural tests ofbilayer samples of FRC and PFC veneers. Essentially rectangular bars of4 mm×3 mm×25 mm were prepared with FRC and either a brittle particulatefilled composite or a soft particulate filled composite. The FRC prepregwas prepared from S2-GLASS® fibers from Owens-Corning, Toledo, Ohio anda dimethacrylate based resin by a filament winding technique. Fibercontent was about 38% by volume. Soft PFC prepreg was an unfilledethoxylated BIS-GMA/PCDMA resin. Brittle PFC prepreg was 78% by weightinorganic barium borosilicate filler and 22% by weight ethoxylatedBIS-GMA/PCDMA resin. Three-point-bending flexural tests were conductedaccording to ADA Specification No. 27. The results are shown in Table 3below.

TABLE 3 Sample Size, mm* Maximum Load (N) Deflection (mm) Top: FRC 3 × 3× 25 274 ± 52 .23 ± .06 Bottom: Brittle PFC 1 × 3 × 25 Top: FRC 3 × 3 ×25 488 ± 17 .50 ± .17 Bottom: Soft FRC 1 × 3 × 25 *thickness, width,length respectively

Average maximum flexural loads were 274±52 Newtons for FRC/brittle PFCbilayers, and 488±17 N for FRC/soft PFC bilayers, indicating more than a75% increase in flexural load bearing capability when a soft PFC veneeris present on the gingival (tensional stress) surface.

EXAMPLE 4

Each PFC is characterized as either brittle or soft according to thedeflection values listed in Table 4 below, which also lists maximum loadfor each sample. Rectangular bars of FRC and PFC material werefabricated for testing flexural strength and deflection using athree-point-bending flexural test. Single and double bars consisting ofFRC and PFC materials were tested. The double bars consisted of a toplayer of FRC material and a bottom layer of PFC material. Both soft andbrittle PFC materials were used in combination with the FRC material bylayering one on the other to form a simulation of a dental restorationhaving an FRC layer and one or more PFC layers. The results are shown inTable 4 below. The results demonstrate that the flexural strength of anFRC/brittle PFC bilayer is higher when force is applied normal to thebrittle PFC (resulting in compressive stress on the brittle PFC), andlower when force is applied normal to the FRC side (resulting in thebrittle PFC being under tensile stress). This result follows from thelower deflection of values of the brittle PFC samples compared to thedeflection values of the FRC samples. It can therefore be concluded thatwhen the brittle PFC layer is under tensile stress, the strength of anFRC/brittle PFC bilayer is limited by the low deflection of the brittlePFC.

TABLE 4 Average Sample Size, mm* Maximum Load (N) Deflection (mm)Brittle PFC 2 × 2 × 25 36.1 ± 4.1 0.5 Soft PFC 2 × 2 × 25 21.6 ± 2.7 4.5FRC 1 × 2 × 25   81 ± 7.7 1.1 Top: FRC 1 × 2 × 25 38.3 ± 5.5 0.5 Bottom:Brittle PFC 1 × 2 × 25 Top: FRC 1 × 2 × 25 76.8 ± 4.8 2.6 Bottom:SoftFRC 1 × 2 × 25 *thickness, width, length respectively

FIG. 5 illustrates a sample 60 having an FRC 62 on the occlusal surfaceand a brittle PFC 64 on the gingival surface (and therefore subject totensile stress) undergoing a three-point-bending flexural test. Thefirst break 66 occurred perpendicular to the X-Z plane of brittle PFC64, and was followed by the delamination 68 of FRC 62 along the X-Zplane. FIG. 6 illustrates sample 70 having FRC 72 on the occlusalsurface and a soft PFC 74 on the gingival surface (and therefore subjectto tensile stress) undergoing a three-point-bending flexural test. Incontrast to the above results, the first break for this sample arosefrom delamination 76 of FRC 72 along the X-Z plane.

Table 4 shows the data for different configurations of test specimensand materials. The average flexural loads were 38.3±5.5 Newtons for theFRC/brittle PFC bilayers and 76.8±4.8 for the FRC/soft PFC bilayers. Thelatter is approaching the average maximum flexural load of 81±7.7 N forFRC material alone. Use of a soft PFC veneer on gingival surface of adental bridge will therefore lead to increased performance of thebridge.

As will be appreciated, the present invention provides a superior resincomposite which is compatible with fiber reinforced composite structuralcomponents and which provides high strength dental restorations.

While various descriptions of the present invention are described above,it should be understood that the various features can be used singly orin any combination thereof. Therefore, this invention is not to belimited to only the specifically preferred embodiments depicted herein.

Further, it should be understood that variations and modificationswithin the spirit and scope of the invention may occur to those skilledin the art to which the invention pertains. Accordingly, all expedientmodifications readily attainable by one versed in the art from thedisclosure set forth herein that are within the scope and spirit of thepresent invention are to be included as further embodiments of thepresent invention. The scope of the present invention is accordinglydefined as set forth in the appended claims.

What is claimed is:
 1. A prosthodontic, comprising: a fiber-reinforcedstructural component comprising a first polymeric matrix and fibersgreater than 100 microns in length; and a veneer, comprising a secondpolymeric matrix in an amount from about 20 to about 60 weight percentof the veneer composition, a randomly dispersed, fibrous filler in anamount from about 5 to about 50 weight percent of the veneercomposition, and a particulate filler in an amount from about 20 toabout 60 weight percent of the veneer composition.
 2. The prosthodonticof claim 1, wherein: the first and second polymeric matrices are thesame or compatible, and are selected from the group consisting ofpolymethacrylates.
 3. The prosthodontic of claim 1, wherein thepolymeric matrix comprises: (a) from about 10 to about 30 weight percentof a dimethacrylate oligomer; (b) from about 65 to about 90 weightpercent of an ethoxylated bisphenol A dimethacrylate having the formula CH₂═C(CH₃)CO₂(C₂H₄O)_(x)C₆H₄C(CH₃)₂C₆H₄(OC₂H₄)_(y)O₂CC(CH₃)═CH₂ whereinx+y is an integer from 2 to 20; and (c) from about 0 to about 40 weightpercent of a diluent monomer for decreasing the viscosity of the dentalresin composition, wherein each of the components (a), (b), and (c) is adifferent monomer and such that the specific amounts with the rangesyield a 100 % by weight polymeric matrix.
 4. The prosthodontic of claim3, wherein the dimethacrylate oligomer is present in an amount fromabout 15 to about 20 weight percent, the ethoxylated bisphenol Adimethacrylate is present in an amount from about 70 to about 80 weightpercent, and the diluent monomer is present in an mount from about 10 toabout 30 weight percent.
 5. The prosthodontic of claim 3, wherein thedimethacrylate oligomer is a urethane dimethacrylate, diurethanedimethacrylate, condensation product of triethylene glycolbis(chloroformate) and 2-hydroxyethylmethacrylate, the condensationproduct of two parts of hydroxyalkylmethacrylate of the formulaH₂C═C(CH₃)C(O)O—A—OH, in which A is a C₁-C₆ alkylene, and 1 part of abis(chloroformate) of the formula ClC(O)—(OR)_(n)—OC(O)Cl, in which R isa C₂-C₅ alkylene having at least two carbon atoms in its principalchain, and n is an integer from 1 to 4, or a mixture thereof.
 6. Theprosthodontic of claim 3, wherein x+y is an integer from 2 to
 7. 7. Theprosthodontic of claim 3, wherein the diluent monomer is a hydroxy alkylmethacrylate, an ethoxylated monomer, or a combination thereof.
 8. Theprosthodontic of claim 7, wherein the diluent monomer is 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, ethylene glycolmethacrylate, diethylene glycol methacrylate, tri(ethylene glycol)dimethacrylate, tetra(ethylene glycol) dimethacrylate,1,6-hexanedioldimethacrylate, or a combination thereof.
 9. Theprosthodontic of claim 8, wherein the diluent monomer is tri(ethyleneglycol) dimethacrylate.
 10. The prosthodontic composition of claim 1,wherein the particulate filler is selected from one or more of a silica,silicate glass, quartz, barium borosilicate, strontium silicate, bariumsilicate, strontium borosilicate, borosilicate, lithium silicate, fumedamorphous silica, calcium phosphate, alumina, zirconia, tin oxide andtitania.
 11. The prosthodontic of claim 1, wherein the fibrous filler isselected from the group consisting of glass, carbon, ceramic, graphite,and polyaramid fibers.
 12. The prosthodontic of claim 1 wherein thefibrous filler comprises fibers having maximum lengths no greater than ¼inch.
 13. The prosthodontic of claim 1 wherein the fibrous fillercomprises fibers having lengths in the range from about 0.1 to about 6mm.
 14. The prosthodontic of claim 1 wherein the fibrous fillercomprises fibers having lengths in the range from about 20 microns toabout 1000 microns.
 15. The prosthodontic of claim 1 wherein the fibrousfiller comprises fibers having diameters in the range from about 5 toabout 10 microns.
 16. The prosthodontic of claim 1 wherein the strain tofailure value of the veneer is about equal to or higher than the strainto failure value of the structural component.
 17. A dental restorationhaving a framework in intimate contact with a veneer, comprising: a softveneer comprising a first polymeric matrix and a first optionalparticulate filler in an amount in the range from about 0 to about 30%by volume; a brittle particulate filled composite veneer comprising asecond polymeric matrix and a second particulate filler; and a fiberreinforced composite framework comprising a third polymeric matrix and afiber filler comprising fibers greater than 100 microns in length,wherein the fiber reinforced composite framework is surrounded by atleast the soft and brittle particulate filled composite veneers, whereinthe soft particulate filled composite veneer is located in therestoration where it is subject to primarily or additionally tensilestrain upon mastication, and the brittle particulate filled veneer islocated in the restoration where it is subject primarily or additionallyto compressive strain.
 18. The dental restoration of claim 17, whereinthe first, second, and third polymeric matrices are the same orcompatible, and are selected from the group consisting of polyamides,polyesters, polyolefins, polyimides, polyacrylates, polymethacrylates,polyurethanes, polymers comprising vinyl ester, epoxy resins,polystyrenes, copolymers comprising styrene and acrylonitrile, ABSpolymers, polysulfones, polyacetals, polycarbonates, and polyphenylenesulfides.
 19. The dental restoration of claim 17, wherein the fiberfiller comprises glass, carbon, graphite, or polyaramid fibers.
 20. Thedental restoration of claim 17, wherein the fiber reinforced compositeframework comprises glass fibers.
 21. The dental restoration of claim17, wherein the first and second particulate fillers are the same ordifferent and are selected from the group consisting of silica, silicateglass, quartz, barium silicate, strontium silicate, barium borosilicate,strontium borosilicate, borosilicate, lithium silicate, amorphoussilica, ammoniated or deammoniated calcium phosphate, alumina, zirconia,tin oxide, titania, and poly(methacrylate).
 22. The dental restorationof claim 17, wherein the soft composite veneer has a greater strain tofracture value than that of the fiber reinforced composite.
 23. Thedental restoration of claim 17, wherein the soft composite veneer hasdeflection values in the range from about 0.6 to about 5.0 mm whenmeasured on a sample of 2 mm×2 mm×25 mm by American NationalStandard/American Dental Association Specification No.
 27. 24. Thedental restoration of claim 17, wherein the brittle particulate filledcomposite comprises from about 70 to about 80% by weight filler.
 25. Thedental restoration of claim 17, wherein the brittle particulatecomposite layer has a higher compressive strength than that of the fiberreinforced composite.
 26. The dental restoration of claim 17, whereinthe brittle particulate filled composite veneer has deflection values inthe range from about 0.3 to about 0.5 mm when measured on a sample of 2mm×2 mm×25 mm by American National Standard/American Dental AssociationSpecification No.
 27. 27. A dental restoration having a framework inintimate contact with a veneer, comprising: a soft particulate filledcomposite veneer comprising a first polymeric matrix and a particulatefiller; a fiber reinforced composite framework comprising a secondpolymeric matrix and a fiber filler comprising fibers greater than 100microns in length, wherein the soft particulate filled composite veneeris located in the restoration where it is subject to primarily oradditionally tensile stresses.
 28. The dental restoration of claim 17,wherein the first and second polymeric matrices are the same orcompatible, and are selected from the group consisting of polyamides,polyesters, polyolefins, polyimides, polyacrylates, polymethacrylates,polyurethanes, polymers comprising vinyl ester, epoxy resins,polystyrenes, copolymers comprising styrene and acrylonitrile, ABSpolymers, polysulfones, polyacetals, polycarbonates, and polyphenylenesulfides.
 29. The dental restoration of claim 27, wherein the fiberfiller comprises glass, carbon, graphite, or polyaramid fibers.
 30. Thedental restoration of claim 27, wherein the fiber reinforced compositeframework comprises glass.
 31. The dental restoration of claim 26,wherein the particulate filler is selected from the group consisting ofsilica, silicate glass, quartz, barium silicate, strontium silicate,barium borosilicate, strontium borosilicate, borosilicate, lithiumsilicate, amorphous silica, ammoniated or deammoniated calciumphosphate, alumina, zirconia, tin oxide, titania, andpoly(methacrylate).
 32. The dental restoration of claim 27, wherein thesoft particulate filled composite comprises filler in an amount in therange from about 10 to about 30% by volume.
 33. The dental restorationof claim 27, wherein the soft particulate composite veneer has a greaterstrain to fracture value than that of the fiber reinforced composite.34. The dental restoration of claim 26, wherein the soft particulatefilled composite veneer has deflection values in the range from about0.6 to about 1.0 mm when measured on a sample of 2 mm×2 mm×25 mm byAmerican National Standard/American Dental Association Specification No.27.
 35. The prosthodontic of claim 1, wherein: the first and secondpolymeric matrices are the same or compatible, and are selected from thegroup consisting of polyamides, polyesters, polyolefins, polyimides,polyacrylates, polymethacrylates, polyurethanes, polymers comprisingvinyl ester, epoxy resins, polystyrenes, copolymers comprising styreneand acrylonitrile, acrylonitrile butadiene styrene polymers,polysulfones, polyacetals, polycarbonates, and polyphenylene sulfides.36. The prosthodontic of claim 27, wherein: the first polymeric matrixand second polymeric matrices are the same or compatible, and areselected from the group consisting of polyamides, polyesters,polyolefins, polyimides, polyacrylates, polymethacrylates,polyurethanes, polymers comprising vinyl ester, epoxy resins,polystyrenes, copolymers comprising styrene and acrylonitrile,acrylonitrile butadiene styrene polymers, polysulfones, polyacetals,polycarbonates, and polyphenylene sulfides.
 37. The dental restorationof claim 27, wherein the fiber filler comprises glass, carbon, graphite,or polyaramid fibers.
 38. The dental restoration of claim 27, whereinthe fiber filler is glass.
 39. The dental restoration of claim 27,wherein the particulate filler is selected from the group consisting ofsilica, silicate glass, quartz, barium silicate, strontium silicate,barium borosilicate, strontium borosilicate, borosilicate, lithiumsilicate, amorphous silica, ammoniated or deammoniated calciumphosphate, alumina, zirconia, tin oxide, titania, andpoly(methacrylate).
 40. The dental restoration of claim 27, wherein thesoft particulate filled composite comprises filler in an amount in therange from about 10 to about 30% by volume.
 41. The dental restorationof claim 27, wherein the soft particulate composite veneer has a lowerstrain to fracture value than that of the fiber reinforced composite.42. The dental restoration of claim 27, wherein the soft particulatefilled composite veneer has deflection values in the range from about0.6 to about 1.0 mm when measured on a sample of 2 mm×2 mm×25 mm byAmerican National Standard/American Dental Association Specification No.27.
 43. The prosthodontic of claim 27, wherein: the first and secondpolymeric matrices are the same or compatible, and are selected from thegroup consisting of polymethacrylates.
 44. The prosthodontic of claim17, wherein: the first, second and third polymeric matrices are the sameor compatible, and are selected from the group consisting ofpolymethacrylates.